Performance of commercial PV device panels in 2016a.
In this chapter, we present a detailed design study of a novel, scalable, self‐contained solar powered electrolytic sodium (Na) metal production plant meant to enable a hydrogen (H2) fuel, sustainable, closed clean energy cycle. The hydrogen fuel is generated on demand inside a motor vehicle using an efficient hydrogen generation apparatus that safely implements a controlled chemical reaction between either ordinary salinated (sea) or desalinated (fresh) water and sodium metal. The sodium hydroxide (NaOH) byproduct of the hydrogen generating chemical reaction is stored temporarily within the hydrogen generation apparatus and is recovered during motor vehicle refueling to be reprocessed in the self‐contained sodium (Na) metal production plant. The electric power for NaOH electrolysis is produced using photovoltaic (PV) device panels spatially arrayed and electrically interconnected on a tower structure that maximizes the use of scarce land area. Our analysis shows that the scalable, self‐contained sodium (Na) metal production plant using solar power is technically and economically viable for meeting the hydrogen fuel clean energy needs of all the motor vehicles in the U.S.A. by constructing approximately 450,000 scalable, self‐contained sodium (Na) metal production plant units in the southwestern desert region that includes West Texas, New Mexico, Arizona and Southern California.
- Sodium metal
- Sodium metal production plant
- Sodium hydroxide
- Sodium hydroxide electrolysis
- Solar powered electrolysis
- Safe hydrogen generation
- Hydrogen clean energy cycle
There is a need in the modern world for sustainable means of producing clean energy economically, on a very large scale. The planet's human population is inexorably increasing toward the 10 billion mark [1–3]. The rapid growth in population presents both opportunities for companies seeking to broaden markets for their products, and challenges for governments, as the growing populations demand their share of prosperity. It is well known that prosperity generating economic growth requires energy [4–6]. To meet the demands for prosperity, carbon based fossil fuel consumption has increased accordingly, resulting in unacceptable levels of air pollution in major conurbations in both advanced and developing countries [7–10]. Much of the pollution comes from burning fossil fuels inside internal combustion engines (ICEs) of motor vehicles and ships. Coal burning thermal power plants used for electricity generation also contribute substantially to the rise in air pollution [11, 12].
Scientific research has hitherto yielded various solutions to the clean energy challenge using innovative approaches ranging from development of hybrid gasoline‐electric motor vehicles (HEVs), plug‐in hybrid gasoline‐electric motor vehicles (PHEVs), pure battery electric vehicles (BEVs), fuel cell electric vehicles (FCEVs), advanced catalysts for reducing exhaust emissions as well as carbon capture technologies applicable to coal burning thermal power plants [13–17]. These solutions however, work only to mitigate the problem of carbon based fossil fuel emissions and do not address the fundamental problem, namely, how to circumvent carbon based fossil fuels in energy generation and ground transport applications. Although HEV, PHEV, BEV and FCEV technologies offer promise in reducing pollution at least locally, they represent at best, an incomplete remedy to a major problem. HEVs and PHEVs still require combustion of gasoline inside an ICE while BEVs require copious quantities of electrical energy for battery charging, generated by power plants connected to the electric grid. The power plants supplying the electric grid can be hydroelectric or nuclear, but far more often, are fossil fuel burning thermal power plants that are only incrementally more efficient than internal combustion engines in motor vehicles . Since hydroelectric generating capacity in the United States of America (U.S.A.) has already been reached and construction of new nuclear power stations is fraught due to well substantiated fears of radiological leaks, it becomes apparent that the only way to meet the increased demand for electricity from electric vehicle proliferation is by constructing more fossil fuel burning thermal power plants [19, 20].
The FCEVs exist at present in small numbers as vehicle prototypes that function primarily as technology demonstrators [21, 22]. FCEVs are unique however, because they represent the only motor vehicle technology that uses hydrogen (H2) fuel to generate electric energy to power a motor driving the wheels of the vehicle. Although in existence in various forms since the 1960s, FCEVs have not proliferated for manifold reasons, the principal ones being the absence of means for safely storing hydrogen fuel on board, coupled with a lack of means to economically generate sufficiently pure hydrogen (H2(g)) fuel to prevent poisoning sensitive catalysts that might be present in the fuel cells [23, 24]. The existing methods of storing hydrogen on board motor vehicles utilize cryogenic storage of liquid hydrogen (H2(l)), storage of hydrogen (H2(g)) gas at pressures as high as 70 MPa (10,153 psi) in cylinders made from composite material, and storage as a metal hydride (MHX) in tanks filled with porous metal sponge or powder comprised of light group 1 and 2 metals and/or transition metal elements, namely, Titanium (Ti) or Nickel (Ni) [25–30]. Such direct hydrogen storage methods however, are impractical due to the high cost of suitable transition metals Ti and Ni, and moreover, because an infrastructure is needed to supply hydrogen directly in large volume to fill liquid or gas tanks or to saturate or replenish the metal sponge within the storage reservoir inside a motor vehicle, a procedure fraught with all of the well known safety risks associated with handling large volumes of elemental hydrogen [31, 32]. Furthermore, the existing industrial method of generating hydrogen (H2(g)) gas using steam reforming of natural gas, the latter containing mostly methane (CH4), produces significant quantities of carbon monoxide (CO) even after application of the shift reaction, the latter meant to transform the CO into carbon dioxide (CO2) [33, 34]. The presence of even minute quantities of CO on the parts per million (ppm) order of magnitude in H2(g) fuel, results in rapid poisoning of sensitive platinum (Pt) catalysts present in the latest generation of low operating temperature, proton exchange membrane (PEM) fuel cells . Catalysts based on a mixture of platinum and ruthenium (Pt‐Ru) developed to overcome the sensitivity of pure Pt to carbon monoxide poisoning are not cost effective for large scale application in motor vehicle transport applications due to the dearth of ruthenium . Since hydrogen production by conventional steam reforming methods generates significant quantities of CO and CO2, it becomes difficult to justify using the approach to generate hydrogen (H2) fuel for FCEVs given that the purpose of advancing such technology is to eliminate carbon based fossil fuel emissions.
Despite challenges, hydrogen (H2) which is stored in near limitless quantity in seawater is the only alternative fuel that is more abundant and environmentally cleaner with the potential of having a lower cost than nonrenewable carbon based fossil fuels. We have shown in previous published work that a novel apparatus and method for safely generating hydrogen fuel at the time and point of use from ordinary salinated (sea) or desalinated (fresh) water (H2O) will enable a vehicle range exceeding 300 miles per fueling using direct combustion of the H2 fuel in appropriately configured internal combustion engines of the Otto or Diesel types, which is comparable to the vehicle ranges presently achieved with gasoline or Diesel fuels, while providing a sustainable, closed clean energy cycle . The novel hydrogen generation apparatus enables hydrogen (H2(g)) fuel to be produced on demand in the motor vehicle using a controlled chemical reaction where liquid water (H2O(l)) is made to react with solid sodium (Na(s)) metal reactant to produce hydrogen (H2(g)) gas and sodium hydroxide (NaOH(s)) byproduct according to Eq. (1).
The high purity hydrogen (H2(g)) fuel produced on demand by the novel hydrogen generation apparatus can be used to safely power FCEVs without contaminating the sensitive Pt catalysts present in PEM fuel cells or any other types of catalysts in fuel cells, because the hydrogen is not derived from carbon based fossil fuels, and therefore does not contain even trace amounts of carbon monoxide or sulfur compounds. The seawater reactant can be concentrated to as much as 252.18 grams of sea salt solute per kilogram of seawater solution to provide a fusion temperature
In this chapter, we describe in detail our company's design approach for constructing a novel, scalable, self‐contained electrolytic sodium (Na) metal production plant that uses electric power sourced from the sun. The solar powered electrolytic production plant is meant to form an integral part of a hydrogen fuel, sustainable, closed clean energy cycle in conjunction with the novel, hydrogen generation apparatus, enabling Na metal to be produced cost effectively without negative impact to the environment .
2. Sodium metal production plant characteristics
For its successful implementation, the hydrogen fuel, sustainable, closed clean energy cycle requires a means of producing quantities of sodium (Na) metal cost effectively on a large scale by electrolysis of sodium hydroxide (NaOH), the latter created as a byproduct of hydrogen (H2(g)) fuel generation inside motor vehicles according to Eq. (1). The electrolysis is performed either on pure sodium hydroxide (NaOH) or on a mixture of NaOH and sea salt, the latter consisting primarily of sodium chloride (NaCl), according to Eqs. (2) and (3) [40–42].
The electrical cost of electrolysis can be estimated from the standard reduction potentials of the oxidation and reduction half reactions that occur at the anode and cathode, respectively of the electrolysis cell when implementing Eqs. (2) and (3) .
From Eqs. (4)–(6), the minimum potentials of
In the United States of America, the only clean renewable source of energy available in sufficient abundance to implement Eqs. (2) and (3) on a large scale is the radiant energy from the sun that illuminates vast tracts of flat, arid, desert land in West Texas, New Mexico, Arizona and Southern California. The weather in the southwestern U.S.A. is mostly warm and arid with high solar irradiance all year and therefore, constitutes the ideal location for constructing scalable, self‐contained solar powered electrolytic sodium (Na) metal production plant units by the thousands [44–48]. Each sodium (Na) metal production plant has to be capable of operating autonomously as a self‐contained factory, requiring minimal maintenance and resources. The diagram showing all of the material and energy inputs and outputs of the self‐contained sodium (Na) metal production plant is presented in Figure 1.
In Figure 1, electric power for the Na metal production plant is produced using photovoltaic (PV) device panels spatially arrayed and electrically interconnected on a vertical tower structure that maximizes the use of scarce real estate or land area. Up to
The self‐contained sodium (Na) metal production plant shown in Figure 2, consists of a solar tower that comprises a photovoltaic (PV) device panel array active area given as
Many factors influence the production yield of sodium (Na) metal during a normal day of plant operation. The two most important factors include the power conversion efficiency of the PV device panels and the magnitude and duration of solar irradiance incident on the PV panels. Other factors affecting the Na metal yield include the power conversion efficiency of the voltage step down DC‐DC converter and the efficiency of the electrolytic cell in recovering the Na metal from fused NaOH(l) or from a mixture of fused NaOH(l) and NaCl(l). The efficiency of the voltage step down DC‐DC converter depends mainly on how much power is dissipated or lost in the solid state transistors as a result of high frequency on‐off switching. The efficiency of the electrolytic cell in this work is viewed in terms of the number of electrons from the electrolytic cell current
2.1. Scalable photovoltaic tower concept
The solar tower comprising the photovoltaic (PV) device panel array supplies electric power to the sodium (Na) metal producing electrolytic cells. The amount of electric energy supplied by the solar tower is a key determinant of the quantity of Na metal that can be electrochemically separated from the NaOH reactant. The energy conversion efficiency of the photovoltaic (PV) device panels is therefore a critical parameter for determining the amount of Na metal that can be produced by the self‐contained sodium (Na) metal production plant. Ideally, the photovoltaic (PV) device panels of the solar tower should have maximum optical to electric energy conversion efficiency approaching the thermodynamic limit
|PV panel technology||PV panel area (m2)||Module efficiency (%)|
|Sunpower SPR‐X21‐345||Monocrystalline Si||1.63||21.5||68.2||57.3||6.02||6.39|
|Suntech STP290S‐20||Monocrystalline Si||1.63||17.8||39.8||31.7||9.15||9.55|
|LG LG280S1C‐B3||Monocrystalline Si||1.64||17.1||38.8||31.9||8.78||9.33|
|First Solar FS‐4117‐2||Thin film CdTe||0.72||16.3||88.2||71.2||1.65||1.79|
|Sharp NU‐U240F2||Monocrystalline Si||1.63||14.7||37.4||30.1||7.98||8.65|
In Table 1, the PV device panels from the Sunpower manufacturing company stand out as having the highest efficiency, due to the use of back‐illumination of the silicon device layer. Multijunction devices that offer higher efficiencies remain at a research and development stage and have not reached a level of maturity or cost effectiveness to be ready for release as commercial PV panel products . Our company, AG STERN, LLC is researching the development of advanced, high efficiency PV devices based on novel, very high transmittance, back‐illuminated, silicon‐on‐sapphire semiconductor substrates expected capable of transmitting 93.7% of the total solar irradiance into the semiconductor device layer and therefore capable of achieving an energy conversion efficiency
The solar tower providing power to the electrolytic cells must be scalable in electric power output, and thus capable of allowing PV device panels to be replaced as higher efficiency ones become available, without affecting the overall operation of the self‐contained Na metal production plant in any way, other than increasing the Na metal yield. Since the highest performing PV device panels currently offered commercially are listed in Table 1, it is possible to calculate the expected power output of the solar tower comprising a PV device panel array active area of
It is clear in Figure 3, that single junction, monocrystalline silicon PV devices having an efficiency
2.2. Solar irradiance conditions
The electric power output of the solar tower comprising photovoltaic (PV) device panels depends on the magnitude and duration of solar irradiance incident on the PV panels, in addition to the PV device energy conversion efficiency described in Section 2.1. It can be assumed that the PV device energy conversion efficiency is constant and might only decrease in value slowly over time . In contrast, the solar irradiance incident on the PV device panels can vary on a daily basis and is determined by two principal factors, namely, the solar geometry and prevailing atmospheric or meteorological conditions.
The sun is effectively a large hydrogen (H2) fusion reactor, spherical in shape with a radius
The solar geometry has a key role in determining how much radiant energy from the sun will be incident on the PV devices located on earth. To understand how the solar geometry influences the solar irradiance at the earth's surface, it will be assumed that earth follows a stable elliptical orbit around the sun described by Eq. (7) .
In Eq. (7), the distance
The solar declination angle
In Eq. (8),
In Eq. (9), the solar declination angle
The PV devices can only generate significant electric power during daylight hours therefore, it is essential to verify that a specific geographic location on earth as defined by the latitude
The relation between the AST and LST can be made using Eq. (11) that includes the ET and longitude correction which accounts for the fact that the sun traverses 1° of longitude in 4 minutes.
In Eq. (11), the local longitude
In Eq. (12), the multiplier of 15° arises because the earth rotates around its own axis 15° in 1 hour, and the AST has a value 0 < AST < 24 hours. When the sun reaches its maximum angle of elevation at the longitude of the observer, it corresponds to the
The Eq. (14) uses the convention of the solar azimuth angle defined as positive clockwise from north meaning that east corresponds to 90°, south corresponds to 180° and west corresponds to 270°. The solar azimuth angle provided by Eq. (14) should be interpreted as 0° ≤
In Eq. (15), the hour angle
The Eq. (16) is applicable for the northern hemisphere while Eq. (17) is applicable for the southern hemisphere. Formulations for the solar declination, elevation, azimuth and zenith angles which account with greater accuracy for the elliptic nature of earth's orbit around the sun exist in the scientific literature often as part of solar position algorithms however, they can be rather complex [71–76]. The air mass can be calculated as a function of the true solar zenith angle
The direct normal total (spectrally integrated) solar irradiance as a function of the air mass (AM) and atmospheric conditions that include the effects of elevation, can be calculated using the Parameterization Model C developed by Iqbal, given in Eq. (19) [78–80].
In Eq. (19),
In Eq. (19), the symbol
In Eqs. (21), (23) and (25), AMa represents the air mass at the actual atmospheric pressure
The Eq. (26) can be used to calculate the atmospheric pressure
In Table 2, geographic and climate characteristics are specified for four prospective locations of the scalable, self‐contained solar powered electrolytic sodium (Na) metal production plant including El Paso, Texas; Alice Springs, Australia; Bangkok, Thailand and Mbandaka, Democratic Republic of Congo (DRC).
|aGeographic coordinates ||bMean monthly temperature ||cMean annual precipitable water ||Mean annual |
|El Paso||+31.807°, –106.377°/ 1206||17.7||1.27||1.27|
|Alice Springs||–23.807°, +133.902°/ 545.2||20.5||1.9||1.16|
|Bangkok||+13.693°, +100.75°/ 1.524||28.2||4.52||1.08|
|Mbandaka||+0.0225°, +18.288°/ 316.9||25.1||3.81||1.04|
In Table 2, the geographic coordinates use the sign convention of +/– latitude
3. Sodium metal production plant architecture
The architecture of the self‐contained sodium (Na) metal production plant has to provide an optimal balance between high performance, reliability and cost effective operation. The highest performance can be achieved by constructing the solar tower of the plant shown in Figure 2, in a manner that allows the optical k‐vectors from the sun to be normally incident onto the photovoltaic (PV) device panels throughout the entire period of daylight from sunrise to sunset. The Figure 4 shows a solar tower architecture with fixed PV device panels, wherein the panels can rotate and tilt with the solar tower as a single unit to follow the sun's overhead trajectory.
In Figure 4, the solar tower is fabricated using modular sections comprised of high strength, lightweight aluminum alloy that can be fitted end to end and bolted together until the final slant height of the structure
3.1. Electrical design of the solar tower
The electrical design of the solar tower comprising PV device panels has to accommodate scalability in the power output level, where it is possible to supplant the existing PV device panels with newer and more efficient ones when they become available, without having to modify other components in the solar tower. It is therefore necessary to optimally dimension the electrical conductors embedded within the branches and central column that transmit the electric power generated by the photovoltaic (PV) device panels to the electrolytic cells, according to the magnitude of the current expected to be transmitted once
In the circuit models shown in Figure 5,
The Eq. (27), can be derived from the circuit model in Figure 5 by short circuiting the output terminals of the solar tower where
The solar tower must be capable of transmitting
In Figure 6, each branch section supports the installation of 2 groups of 15 series connected PV panels having an efficiency
The electric current from each branch section flows into the electrical conductors installed inside the central column of the solar tower as shown in Figure 6. Therefore, electric current that flows from the outermost branch section toward the central column increases as each branch section contributes additional current generated by the 30 PV panels mounted on it. If an ASTM direct normal AM 1.5D standard terrestrial solar spectral irradiance with a total irradiance
The four electrical conductors installed within the modular sections of the central column of the solar tower that are located at or near the top of the solar tower, do not have to carry the maximum current
The electrical design of the solar tower described provides manifold advantages including a mostly parallel electrical interconnection architecture for the PV device panels that allows the MPP of the PV device panels to be controlled collectively by controlling the output voltage
3.2. Electrical design of the sodium hydroxide electrolysis plant
The solar tower apparatus described in Section 3.1 implements a mostly parallel electrical interconnection architecture for the PV device panels that yields two identical, independent and electrically isolated low voltage DC power supplies, each having a maximum voltage
In a fused or molten state, NaOH(l) is highly corrosive and therefore the only conventional materials capable of withstanding prolonged exposure to its caustic effects at an elevated temperature include graphite, iron and nickel. Graphite however, cannot be used as an anode electrode because it will react with the oxygen (O2) generated to produce carbon dioxide (CO2) and become consumed in the process. Iron can withstand corrosion from fused NaOH(l), and consequently could be used to fabricate the electrolytic vessel however, as an anode electrode, the reaction with steam (H2O(g)) and O2 will quickly oxidize and erode iron. The only material suitable for fabricating both the anode and cathode electrodes remains nickel (Ni) which is significantly more expensive than both graphite and iron. The cost of the Ni electrodes therefore becomes an important factor in limiting the maximum current in the electrolytic cell. The other factor limiting the current in the electrolytic cell becomes the PWM DC‐DC converter that must supply the large currents at the correct output voltage to the electrolytic cell, safely and reliably.
It is necessary to provide two identical voltage step down PWM DC‐DC converters to convert the power
The design of voltage step down PWM DC‐DC converters that have a fixed output voltage
The synchronous parallel multiphase voltage step down PWM DC‐DC converter power supply shown in Figure 7 offers the inherent advantage of allowing the large load current
Assuming the ideal case that current sharing between synchronous parallel voltage step down converter circuits is equal, then
The synchronous parallel multiphase voltage step down PWM DC‐DC converter power supply in Figure 7 with
The control system for the multiphase voltage step down PWM DC‐DC converter shown in Figure 8 consists of a sensor that senses the process parameter to be controlled, namely, the input voltage
The electronic circuits shown in Figure 9 are representative of the functional blocks of the PWM DC‐DC converter control system. The sensor circuit can consist of a resistive voltage divider with a unity gain op‐amp buffer that senses the voltage
The error amplifier subtracts the input voltage
The PID unit receives the error voltage
In Eq. (33), the terms
It is possible to gain insight into the operation of the synchronous parallel multiphase voltage step down PWM DC‐DC converter with attached solar tower PV device panel array, from the most common modeling approach using small signal analysis based on state space averaging . The open loop transfer function
The state space form of the above four differential equations describing the PWM DC‐DC converter having just a single phase
The Eq. (38), has the form , and Eq. (39) has the form . The averaged state space equation can be expressed in a similar form , where the
When all transients in the PWM DC‐DC converter have stabilized and steady state operation is achieved, then , thus the averaged state space equation can be used to express the DC steady state equations given as Eqs. (40) and (41).
The result in Eq. (43) allows to calculate the DC value duty cycle
The linear model of the open loop transfer function
Taking the Laplace transform of the averaged state space equation which has the form , yields the result in Eq. (47).
In Eq. (47),
The analysis to yield the open loop transfer function for the multiphase voltage step down PWM DC‐DC converter with
In Eq. (52), the matrices
4. Sodium metal production plant operating characteristics
The solar cycle described in Section 2.2, the electrical design of the solar tower described in Section 3.1, and the electrical design of the sodium hydroxide (NaOH) electrolysis plant described in Section 3.2, entail that the voltage step down pulse width modulated (PWM) DC‐DC converter supplying electricity from the solar tower PV device panel array directly to the NaOH electrolytic cells has to be operated according to a precise protocol.
Prior to sunrise occurring, the sodium hydroxide (NaOH) electrolytic cells are replenished to capacity with concentrated aqueous NaOH(aq) solution from the storage tanks shown in Figure 2, that are located adjacent to the Q‐type metal building that houses electrical switch gear, voltage step down (PWM) DC‐DC power converter units, the sodium hydroxide (NaOH) electrolytic cells, sodium (Na) metal packaging unit and chlorine (Cl2) gas separation and bottling unit. As sunrise commences, the solar tower photovoltaic (PV) device panel array begins generating electric power. The voltage step down PWM DC‐DC converter supplies the electric power from the solar tower PV device panel array to the electrolytic cells at a fixed voltage given as
The electric current is supplied to the 25 electrolytic cells electrically connected in series, by the synchronous parallel multiphase voltage step down PWM DC‐DC converter at a fixed output voltage set by the utility scale battery given as
The sodium (Na) metal production plant can effectively be controlled using only two adjustable parameters, including the set point reference voltage
It is possible to calculate the quantity of Na metal produced throughout the year by the self‐contained sodium (Na) metal production plant sited in the different geographic locations given in Table 2, based on the hours of daylight and the prevailing air mass conditions. It is not necessary to specify a detailed design for the NaOH electrolytic cell to generate an accurate daily estimate of Na metal production yield throughout the year, if it is assumed that maximum electric power available from the solar tower PV device panel array can always be supplied to the electrolytic cells by appropriately controlling the electrical resistance of the NaOH electrolytic cells together with the set point reference voltage
The calculation in Figure 10 provides the expected daily sodium (Na) metal production yield under the assumption that the energy conversion efficiency
5. Logistics of sodium hydroxide and sodium metal
For the full benefits of the hydrogen (H2(g)) fuel based sustainable clean energy economy to be realized, it is essential to overcome the logistical problems inherent with H2(g) fuel. The H2(g) fuel possesses the unique characteristic that it can be combusted directly inside an internal combustion engine (ICE) to produce useful work without emission of carbon dioxide (CO2) or sulfur oxides (SOX) and with minimal emission of nitrogen oxides (NOX). It can also be converted to electricity directly in a fuel cell to produce useful work with substantially higher efficiency than in an ICE. Regardless of how the versatile H2(g) fuel is applied to produce useful work, it is essential to provide safe, reliable and economical logistics for its use. The major drawback of H2(g) fuel remains the difficulty of direct storage. Fortunately, the element sodium (Na) positioned two rows below hydrogen in Group I of the periodic table of elements, is sufficiently electropositive to be capable of chemically releasing the H2(g) fuel stored in either ordinary salinated (sea) or desalinated (fresh) water (H2O) over a wide temperature range . Sodium (Na) is also sufficiently abundant in nature in the form of sodium chloride (NaCl) in seawater, to make its use economical for H2(g) fuel generation . Therefore, sodium (Na) metal and the sodium hydroxide (NaOH) byproduct resulting from the H2(g) fuel producing chemical reaction in Eq. (1), constitute the ideal intermediate materials needed to render H2(g) into a practical and usable fuel by storing the sun's radiated energy as Na metal.
A hydrogen (H2(g)) fuel clean energy economy based on a sustainable, closed clean energy cycle that uses sodium (Na) metal recovered by electrolysis from sodium hydroxide (NaOH) as a means of storing the sun's radiant energy collected during daytime hours, provides numerous benefits including safe, reliable and economical logistics. The scalable, self‐contained sodium (Na) metal production plant that stores the sun's radiant energy in sodium (Na) metal, can be constructed in almost any geographic location on earth benefitting from ample solar irradiance and clear weather all year. In the U.S.A., the arid, southwestern desert region offers the requisite conditions, including sufficient undeveloped land area to construct scalable, self‐contained solar powered electrolytic sodium (Na) metal production plants by the thousands. Using the southwestern desert region that includes West Texas, New Mexico, Arizona and Southern California as a hub for solar powered sodium (Na) metal production by electrolysis of sodium hydroxide (NaOH), it is possible to develop sufficient Na metal production capacity based on the scalable, self‐contained sodium (Na) metal production plant described, to meet the U.S.A.'s energy needs for motor vehicle transport and for broader clean electric power applications.
The physical and chemical properties of sodium (Na) metal and sodium hydroxide (NaOH) render these materials ideal from an operational logistical standpoint. The sodium (Na) metal is a solid at room temperature and therefore has negligible vapor pressure. As a result, Na metal can be stored almost indefinitely in hermetically sealed packaging that can be opened much as a sardine can, only when the Na metal must be loaded into a hydrogen generation apparatus to react with either salinated (sea) or desalinated (fresh) water (H2O) according to Eq. (1), to produce hydrogen (H2(g)) fuel on demand . The sodium hydroxide (NaOH) byproduct of the hydrogen producing chemical reaction in Eq. (1), is also a solid at room temperature in its pure form and has negligible vapor pressure. The NaOH is miscible with water in all proportions, enabling the aqueous NaOH(aq) solution to be readily transferred by pumping into and out of sealed tanks for transport by truck, rail car or pipeline to the remotely located self‐contained sodium (Na) metal production plant units for reprocessing by electrolysis according to Eqs. (2) and (3), to recover the Na metal for reuse in generating H2(g) fuel. The NaOH(aq) transportation/storage tanks of the type shown in Figure 2, can be fiberglass or metal with a corrosion resistant internal rubber liner, and must seal hermetically to exclude ambient air that contains carbon dioxide (CO2) which slowly degrades the NaOH(aq), albeit not irreversibly.
To obtain a sense for the magnitude of the logistical effort needed to produce and distribute sufficient sodium (Na) metal to fuel all of the motor vehicles in the U.S.A. while recovering the sodium hydroxide (NaOH) byproduct for reprocessing by electrolysis, it is necessary to consider the total number of vehicles in circulation. According to the Bureau of Transportation Statistics at the United States Department of Transportation (DOT), the total number of registered vehicles in the year 2013 in the U.S.A. numbered 255,876,822 . The figure includes passenger cars, motorcycles, light duty vehicles, other 2‐axle/4‐tire vehicles, trucks with 2‐axles/6‐tires or more and buses. If it is further assumed that each motor vehicle on average consumes the energy equivalent of 16.2 gallons of 100 octane gasoline (2,2,4-Trimethylpentane) per week, then the corresponding quantity of H2(g) fuel having an equivalent heating value is given as 15.8 kg. The generation of 15.8 kg of H2(g) fuel according to Eq. (1), requires that 361.6 kg of Na metal react with approximately 300 kg of water (H2O) . Therefore, the total quantity of Na metal consumed per week in the U.S.A. can be calculated as 255,876,822 vehicles × 361.6 kg/week = 92,525,058,835 kg/week. If each solar tower produces a mass
Our company believes that hydrogen (H2(g)) fuel will earn an important role in motor vehicle transport applications for powering smaller 1–5 kW class secondary power fuel cells for onboard continuous recharging of battery electric vehicles (BEVs), a concept implemented successfully in the 1960s using H2(g) fuel stored in high pressure cylinders . The concept of a smaller hydrogen fuel cell operating at a fixed power output level to continuously recharge an electric storage battery can be extended not only to motor vehicle propulsion systems but also for a broad range of clean electric power applications, including general ground transport that includes commercial trucks, trains, maritime transport as well as powering single family homes, commercial establishments and industrial enterprises. Such an approach will ultimately enable mankind to dispense with use of carbon based fossil fuels for motor vehicle transport applications and most other types of ground based electric power generation.
The technical and economic viability of a novel, scalable, self‐contained solar powered electrolytic sodium (Na) metal production plant has been demonstrated for meeting the hydrogen (H2(g)) fuel clean energy needs of the U.S.A. The scalable, self‐contained sodium (Na) metal production plant uses a solar tower PV device panel array to collect and convert the sun's vast radiant energy emission produced by hydrogen fusion, into electric power that is used to recover sodium (Na) metal from sodium hydroxide (NaOH) or from a mixture of NaOH and NaCl by electrolysis. The Na metal can subsequently be reused to generate H2(g) fuel and NaOH byproduct by reacting with either ordinary salinated (sea) or desalinated (fresh) water (H2O). The scalable, self‐contained sodium (Na) metal production plant operation is enabled by a specially designed voltage step down PWM DC‐DC converter consisting of a multiphase converter topology with up to 32 synchronous voltage step down converter circuits connected in parallel. The PWM DC‐DC converter has a fixed output voltage
|Length of the semi‐major axis of earth's elliptical orbit around the sun||(m)|
|Photovoltaic (PV) panel area||(m2)|
|Photovoltaic (PV) panel array area||(m2)|
|Air mass at mean sea level|
|Air mass at actual atmospheric pressure|
|Solar tower branch length||(m)|
|Solar tower branch section length||(m)|
|Solar tower branch height||(m)|
|DC‐DC converter duty cycle|
|DC‐DC converter duty cycle, |
|DC‐DC converter duty cycle small signal AC perturbation|
|DC‐DC converter duty cycle DC value|
|DC‐DC converter duty cycle DC value, |
|Electrical conductor diameter||(cm)|
|Standard reduction, oxidation half reaction potential||(V)|
|Standard overall reaction potential||(V)|
|Eccentricity correction for the solar constant|
|Proportional circuit gain|
|Integrator circuit gain|
|Differentiator circuit gain|
|DC‐DC converter open loop voltage transfer function|
|Photovoltaic (PV) array elevation above mean sea level||(m)|
|Hours between sunrise and ||(hours)|
|Hours between ||(hours)|
|Direct normal solar irradiance||(W/m2)|
|ASTM direct normal AM 1.5D standard terrestrial total solar irradiance||(W/m2)|
|ASTM global AM 1.5G standard terrestrial total solar irradiance||(W/m2)|
|Solar tower branch current||(A)|
|Solar tower branch section current||(A)|
|Solar tower output current||(A)|
|Solar tower maximum output current||(A)|
|DC‐DC converter per phase output current||(A)|
|DC‐DC converter output current||(A)|
|Electrolytic cell current||(A)|
|Photovoltaic (PV) device current||(A)|
|Photovoltaic (PV) panel short circuit current||(A)|
|Photovoltaic (PV) panel maximum power point current||(A)|
|Photovoltaic (PV) panel array maximum power point current||(A)|
|IGBT collector‐emitter current||(A)|
|Aerosol optical depth or thickness|
|Vertical ozone layer depth or thickness||(cm (NTP))|
|Number of photovoltaic (PV) panels|
|Number of photovoltaic (PV) panels per branch|
|Number of photovoltaic (PV) panels per branch section|
|Number of branches on the left or right of the solar tower|
|Number of branches on the solar tower|
|Number of phases|
|Number of solar towers|
|Day number in a year from 1 to 365|
|Solar tower left or right half output power||(W) or (MW)|
|Solar tower output power||(W) or (MW)|
|Solar tower output power (50 towers)||(W) or (MW)|
|Photovoltaic (PV) panel width||(m)|
|Photovoltaic (PV) panel length||(m)|
|Distance from the center of the sun to the center of the earth||(m)|
|Photovoltaic (PV) device parallel resistance, series resistance||(Ω)|
|Thevenin equivalent resistance||(Ω)|
|Electrolytic cell resistance||(Ω)|
|Solar tower structure height||(m)|
|Solar tower structure width||(m)|
|Absolute temperature, ITS‐90 or Celsius temperature||(K) or (°C)|
|Surface temperature of IC package||(°C)|
|Time period for a cycle|
|Vector, vector DC component|
|Aqueous sodium hydroxide volume||(Gal)|
|Solar tower output voltage||(V)|
|Solar tower maximum output voltage||(V)|
|Solar tower central column conductor voltage drop||(V)|
|DC‐DC converter input voltage||(V)|
|DC‐DC converter output voltage||(V)|
|Utility scale battery voltage||(V)|
|Electrolytic cell voltage||(V)|
|Photovoltaic (PV) panel open circuit voltage||(V)|
|Photovoltaic (PV) single cell maximum power point voltage||(V)|
|Photovoltaic (PV) panel maximum power point voltage||(V)|
|Photovoltaic (PV) panel array maximum power point voltage||(V)|
|Thevenin equivalent voltage||(V)|
|IGBT collector‐emitter voltage||(V)|
|DC‐DC converter scaled input voltage||(V)|
|DC‐DC converter input voltage, set point reference||(V)|
|DC‐DC converter control circuit, error amplifier output||(V)|
|DC‐DC converter control circuit, PID circuit output||(V)|
|Precipitable water thickness at actual atmospheric pressure and temperature||(cm)|
|Vector, vector DC component|
|Solar altitude or elevation angle above the observer's horizon||(°)|
|Maximum solar altitude or elevation angle above the observer's horizon||(°)|
|Solar azimuth angle||(°)|
|Electrolytic cell efficiency||(%)|
|DC‐DC converter efficiency||(%)|
|Photovoltaic (PV) device panel efficiency||(%)|
|Angle between position of earth in orbit around sun and perihelion position||(°)|
|Solar zenith angle||(°)|
|Photovoltaic (PV) plant density||(mi−2)|
|Transmittance by Rayleigh scattering|
|Transmittance by ozone|
|Transmittance by uniformly mixed gases|
|Transmittance by precipitable water vapor|
|Transmittance by aerosol|
|Molar gas constant||8.3144621 (J/K·mol)|
|Molar mass, air||0.028964 (kg/mol)|
|Specific gas constant, air||287.06194 (J/Kċkg)|
|Eccentricity of earth's elliptical orbit around the sun||0.01673|
|Faraday constant||96485.3365 (C/mol)|
|Gravitational acceleration near earth's surface||9.80665 (m/s2)|
|Solar constant||1367 (W/m2)|
|Standard atmospheric pressure||101325 (Pa)|
|Power output of the sun||3.8 × 1026 (W)|
|Power output of the sun reaching the earth||1.7 × 1017 (W)|
|Radius of the sun||6.96 × 108 (m)|
|Mean distance from center of sun to center of earth||1.496 × 1011 (m)|
|Celsius zero point, ITS‐90||273.15 (K)|
|Eutectic temperature of NaCl‐H2O solution||−21.2 (°C)|
|Surface temperature of the solar black body||5800 (K)|
|Period of earth's rotation around the sun||365.24 (days)|
|Period of earth's rotation on its axis (||86,400 (sec)|
|Obliquity or tilt angle of earth's rotation axis||23.44 (°)|
|Solar angle of declination||−23.44 ≤ |
|Thermodynamic efficiency limit of PV device panels||93 (%)|
|Latitude at Tropic of Cancer||+23.44 (°)|
|Latitude at Tropic of Capricorn||−23.44 (°)|
|Longitude at Greenwich Prime Meridian||0 (°)|
|Angular velocity of earth's rotation on its axis||7.292115 × 10−5 (rad/sec)|
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